Exhaust Valve Mod - Little More Rumble at Idle!! - BMW S1000RR Forums: BMW Sportbike Forum
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post #1 of 187 (permalink) Old 02-12-2010, 06:23 PM Thread Starter
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Thumbs up Exhaust Valve Mod - Little More Rumble at Idle!!

MODIFICATION: Perform at your own risk... This modification will disable the valve in the exhaust (at the exit of the cat) such that it stays open 100% of the time, instead of closing at low RPMs. The end result is more Rumble at low RPMs... and it sounds goooood! This would work whether or not you're still using the stock can or if you go to an aftermarket slip-on.

There is a flapper valve on the exit pipe of the Cat right before the slip-on. This particular valve is there in order to pass Noise level requirements from the 0-5000-ish RPMs. This is similar to other bikes - I know my '08 CBR1000RR was the same way.

At the valve, there is a plastic cover. On the side facing you, there is a plastic clip, remove the plastic retaining clip with a screwdriver (removes very easily). Now the plastic cap will come right off. Once off, you will see the two cables that operate the flapper valve (normally closed at idle). Loosen the nut for each cable where they attach to the bracket/valve. Once loose, slide the cable out of its location and release the cable's end from the valve. The next step is easier if you remove the tank side plastics (also requires the top tank plastic to be removed and the seat). There is servo that operates the cables. It's locate under the seat, but you access the cables from below the tail (above the hugger). Remove the cables from the servo with some needle nose pliers or what ever tool you prefer. With a long screw driver from the right side, I was able to pry the cable from it's mount (just to the right of the servo), there are two other clips holding the cables in place, remove the cables from there and then remove the cables. Once this has been done put the cap back on the valve and carefully slide the retaining clip back in. The valve will stay in the 100% open position full time due to it being "spring loaded" to do so. No codes are thrown since the servo is still plugged in and operating normally. Reassemble the plastics, you're done.

Now you got more RUMBLE

EDIT: Per RocketJockey's suggestion, I have now safety wired the valve in the open position. Although it is a strong spring, he heard of someone at the track that only had a few laps to go and went into limp mode because the spring went out on them. Better safe than sorry - so I wired it open.

Picture 1: Valve that is on the exit side of the CAT. I'm pointing at the clip that holds the cover on.


Picture 2: Clip is shown partially removed, when you reinstall you will want to wiggle the cover a little to ensure the clip seated the cover properly (don't want to loose it going down the road).


Picture 3: Valve with the cover off.


Picture 4: Shows where the other end of the cables attach (to the servo motor). This is looking in from the right side of the bike w/the tank plastic removed.
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Last edited by 1000RR; 05-14-2010 at 08:10 PM. Reason: Put Pictures into Post
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post #2 of 187 (permalink) Old 02-12-2010, 06:51 PM
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I thought that was also functional for back pressure at low rpm?
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post #3 of 187 (permalink) Old 02-12-2010, 07:01 PM Thread Starter
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Originally Posted by putyoursoxon View Post
I thought that was also functional for back pressure at low rpm?
It's like the '08/'09 CBR, they did it to pass EPA/Sound requirements.

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Last edited by 1000RR; 03-01-2010 at 10:41 PM.
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post #4 of 187 (permalink) Old 02-12-2010, 07:20 PM
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Quote:
Originally Posted by 1000RR View Post
If it's like the '08/'09 CBR, they did it to pass EPA/Sound requirements. I had heard it was for similar reasons for the BMW.
It is for noise restriction and I'm curious now as to whether or not you are going to throw a code when you turn the key and it runs it's systems check. Let me know! I'm rather curious.
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post #5 of 187 (permalink) Old 02-12-2010, 07:24 PM Thread Starter
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Originally Posted by snocompton View Post
It is for noise restriction and I'm curious now as to whether or not you are going to throw a code when you turn the key and it runs it's systems check. Let me know! I'm rather curious.
EDIT: I hooked up w/my GS911 (17Mar10) and laptop and it is reading a code on the exhaust Flapper Valve. I'm finding out now what folks are doing that are going to full systems.

EDIT [again]: Spoke with a couple BMW mechanics - the consensus is that this code is just a history. The ECU has realized that the operation of the exhaust flapper valve is not normal since the cables are disconnected. The end result is that this particular code will show up when scanned for codes (it cannot be erased at this time, maybe in the future) but will not show up on the dash of the bike and does no harm to anything. FWIW, they also did confirm that this particular valve is only there for EPA-noise requirements.

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Last edited by 1000RR; 04-18-2010 at 10:22 AM.
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post #6 of 187 (permalink) Old 02-12-2010, 08:36 PM
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I will say that I think you will lose some low end torque. Thoughts?

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post #7 of 187 (permalink) Old 02-12-2010, 08:53 PM Thread Starter
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Quote:
Originally Posted by URBAN LEGEND View Post
I will say that I think you will lose some low end torque. Thoughts?
I think all the back pressure your needing is found right in the big a$$ cat box underneath... don't think the valve is gonna make a big difference.

When I did this to my CBR I took the "butt" dyno out before and after and it felt better after... also made a dead spot in the CBR a little better. The valve is open all the way at around 5000... I don't think you'll be getting a big difference either way down below that... all the power kicks in around 7-9K... valves already been open for about 2K RPMs

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post #8 of 187 (permalink) Old 02-12-2010, 11:06 PM
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Pretty sure it is purely for noise levels. The new R1200GS, RT and K1300S all now incorporate these valves. It let's the bikes pass noise emissions. It partially closes at certain RPMs and bike speeds. When the bikes are sent to pass noise emissions I believe they not only do it at idle but also do a pass at highway speed past a decible meter.

The two exhaust valves at the headers are for low end power improvement.
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post #9 of 187 (permalink) Old 02-13-2010, 02:40 AM
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Mmmmm what about smashing the cat honeycomb out as well,i have a slipon coming from Mark and thinking about cutting the cat out and fitting a Y pipe
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post #10 of 187 (permalink) Old 02-13-2010, 09:17 AM Thread Starter
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Originally Posted by Thugsfatboy View Post
Mmmmm what about smashing the cat honeycomb out as well,i have a slipon coming from Mark and thinking about cutting the cat out and fitting a Y pipe
Would be a bit of an effort, but would be GREAT once it's done I'm sure.

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